Oriented polyethylene films and a method for making the same

ABSTRACT

A first oriented film comprising a first polyethylene composition which comprises: from 20 to 50 wt % of a first linear low density polyethylene polymer having a density greater than 0.925 g/cc and an I 2  lower than 2 g/10 min; and from 80 to 50 wt % of a second linear low density polyethylene polymer having a density lower than or equal to 0.925 g/cc and an I 2  greater than or equal to 2 g/10 min; wherein the first polyethylene composition has an 12 from 0.5 to 10 g/10 min and a density from 0.910 to 0.940 g/cc is provided.

CLAIM OF PRIORITY

This application is a Divisional of US § 371 National Stage Application15/302,967, filed Oct. 7, 2016 and published as U.S. Publication No.2017/0029583 on Feb. 2, 2017, which claims priority to InternationalApplication Number PCT/CN2014/074992, filed Apr. 9, 2014 and publishedas WO 2015/154253 on Oct. 15, 2015, the entire contents of which areincorporated herein by reference in its entirety.

FIELD OF INVENTION

The instant invention relates to oriented polyethylene films and amethod for making the same.

BACKGROUND OF THE INVENTION

Tenter frame sequential biaxial orientation process is one of the commonfabrication processes in the polymer film industry. In this process,polymers are oriented in the semi-solid state, which is significantlydifferent from the orientation in the molten state, as occurs intraditional blown film or cast film processes. Most physical properties,including clarity, stiffness and toughness, are dramatically improvedupon the semi-solid state orientation. Polymers that can be processed bythe tenter frame include polypropylene (PP), polyethylene terephthalate(PET), and polyamide (PA). However, currently available polyethylenescannot be oriented by the tenter frame process, due to their poorstretchability.

SUMMARY OF THE INVENTION

The instant invention includes oriented polyethylene films and a methodfor making the same.

In one embodiment, the instant invention provides a first oriented filmcomprising a first polyethylene composition which comprises: from 20 to50 wt % of a first linear low density polyethylene polymer having adensity greater than 0.925 g/cc and an I₂ lower than 2 g/10 min; andfrom 80 to 50 wt % of a second linear low density polyethylene polymerhaving a density lower than 0.925 g/cc and an I₂ greater than 2 g/10min; wherein the first polyethylene composition has an I₂ from 0.5 to 10g/10 min and a density from 0.910 to 0.940 g/cc.

DETAILED DESCRIPTION OF THE INVENTION

The instant invention includes oriented polyethylene films and a methodfor making the same.

A first embodiment provides a first oriented film comprising a firstpolyethylene composition which comprises: from 20 to 50 wt % of a firstlinear low density polyethylene polymer having a density greater than orequal to 0.925 g/cc and an I₂ lower than or equal to 2 g/10 min; andfrom 80 to 50 wt % of a second linear low density polyethylene polymerhaving a density lower than or equal to 0.925 g/cc and an I₂ greaterthan or equal to 2 g/10 min; wherein the first polyethylene compositionhas an I₂ from 0.5 to 10 g/10 min and a density from 0.910 to 0.940g/cc.

The first polyethylene composition comprises from 20 to 50 wt % of afirst linear low density polyethylene polymer. All individual values andsubranges from 20 to 50 percent by weight (wt %) are included herein anddisclosed herein; for example the amount of the first linear low densitypolyethylene polymer can be from a lower limit of 20, 30, or 40 wt % toan upper limit of 25, 35, 45, or 50 wt %. For example, the amount of thefirst linear low density polyethylene polymer can be from 20 to 50 wt %,or in the alternative, from 20 to 35 wt %, or in the alternative, from35 to 50 wt %, or in the alternative from 25 to 45wt %.

The first linear low density polyethylene polymer has a density greaterthan or equal to 0.925 g/cc. All individual values and subranges greaterthan or equal to 0.925 g/cc are included herein and disclosed herein;for example, the density of the first linear low density polyethylenepolymer can be from a lower limit of 0.925, 0.928, 0.931 or 0.34 g/cc.In some aspects of the invention, the first linear low densitypolyethylene polymer has a density less than or equal to 0.98 g/cc. Allindividual values and subranges of less than 0.98 are included hereinand disclosed herein; for example, the first linear low densitypolyethylene polymer can have a density from an upper limit of 0.98,0.97, 0.96 or 0.95 g/cc.

The first linear low density polyethylene polymer has an I₂ less than orequal to 2 g/10 min. All individual values and subranges from 2 g/10 minare included herein and disclosed herein. For example, the first linearlow density polyethylene polymer can have a density from an upper limitof 2, 1.9, 1.8, 1.7, 1.6 or 1.5 g/10 min. In a particular aspect of theinvention, the first linear low density polyethylene polymer has an I₂with a lower limit of 0.01 g/10 min. All individual values and subrangesfrom 0.01 g/10 min are included herein and disclosed herein. Forexamples the first linear low density polyethylene polymer can have anI₂ greater than or equal to 0.01, 0.05, 0.1, 0.15 g/10 min.

The first polyethylene composition comprises from 80 to 50 wt % of asecond linear low density polyethylene polymer. All individual valuesand subranges from 80 to 50 wt % are included herein and disclosedherein; for example, the amount of the second linear low densitypolyethylene can be from a lower limit of 50, 60 or 70 wt % to an upperlimit of 55, 65, 75 or 80 wt %. For example, the amount of the secondlinear low density polyethylene polymer can be from 80 to 50 wt %, or inthe alternative, from 80 to 60 wt %, or in the alternative, from 70 to50 wt % , or in the alternative, from 75 to 60 wt %.

The second linear low density polyethylene polymer has a density lowerthan or equal to 0.925 g/cc. All individual values and subranges lowerthan or equal to 0.925 g/cc are included herein and disclosed herein;for example, the density of the second linear low density polyethylenepolymer can have an upper limit of 0.925, 0.921, 0.918, 0.915, 0.911, or0.905 g/cc. In a particular aspect, the density of the second linear lowdensity polyethylene polymer can have a lower limit of 0.865 g/cc. Allindividual values and subranges equal to or greater than 0.865 g/cc areincluded herein and disclosed herein; for example, the density of thesecond linear low density polyethylene polymer can have a lower limit of0.865, 0.868, 0.872, or 0.875 g/cc.

The second linear low density polyethylene polymer has an I₂ greaterthan or equal to 2 g/10 min. All individual values and subranges from 2g/10 min are included herein and disclosed herein; for example, the I₂of the second linear low density polyethylene polymer can have a lowerlimit of 2, 2.5, 5, 7.5 or 10 g/10 min. In a particular aspect, thesecond linear low density polyethylene polymer has an I₂ of less than orequal to 1000 g/10 min.

The first polyethylene composition has an I₂ from 0.5 to 10 g/10 min.All individual values and subranges from 0.5 to 10 g/10 min are includedherein and disclosed herein; for example the I₂ of the firstpolyethylene composition can be from a lower limit of 0.5, 1, 4, 7, or 9g/10 min to an upper limit of 0.8, 1.6, 5, 8 or 10 g/10 min. For examplethe I₂ of the first polyethylene composition can be from 0.5 to 10 g/10min, or in the alternative, from 0.5 to 5 g/10 min, or in thealternative, from 5 to 10 g/10 min, or in the alternative, from 2 to 8g/10 min, or in the alternative, from 3 to 7 g/10 min.

The first polyethylene composition has a density from 0.910 to 0.940g/cc. All individual values and subranges from 0.910 to 0.940 g/cc areincluded herein and disclosed herein; for example, the density of thefirst polyethylene composition can be from a lower limit of 0.91, 0.92,or 0.93 g/cc to an upper limit of 0.915, 0.925, 0.935 or 0.94 g/cc. Forexample, the density of the first polyethylene composition can be from0.910 to 0.940 g/cc, or in the alternative, from 0.91 to 0.925 g/cc, orin the alternative, from 0.925 to 0.94 g/cc, or in the alternative, from0.92 to 0.935 g/cc.

The invention further provides the first oriented film according to anyembodiment disclosed herein except that the first and/or second linearlow density polyethylene polymer(s) is produced using a Ziegler-Nattacatalyst.

The invention further provides the first oriented film according to anyembodiment disclosed herein except that the first linear low densitypolyethylene polymer has a density greater than or equal to 0.930 g/ccand an I₂ lower than 1 g/10 min.

The invention further provides the first oriented film according to anyembodiment disclosed herein except that the second linear low densitypolyethylene polymer has a density less than 0.920 g/cc and an I₂greater than 4 g/10 min.

In another embodiment, the invention provides a second oriented filmcomprising a second polyethylene composition which comprises: from 50 to80 wt % of a third linear low density polyethylene polymer having adensity greater than 0.925 g/cc and an I₂ less than 2 g/10 min; and from50 to 20 wt % of a fourth linear low density polyethylene polymer havinga density lower than 0.920 g/cc and an I₂ greater than 2 g/10 min;wherein the second polyethylene composition has an I₂ from 0.5 to 10g/10 min and a density from 0.910 to 0.940 g/cc.

The second polyethylene composition comprises from 50 to 80 wt % of athird linear low density polyethylene polymer. All individual values andsubranges from 50 to 80 wt % are included herein and disclosed herein;for example, the amount of third linear low density polyethylene polymercan be from a lower limit of 50, 60, or 70 wt % to an upper limit of 55,65, 75 or 80 wt %. For example, the amount of the third linear lowdensity polyethylene polymer can be from 50 to 80 wt %, or in thealternative, from 60 to 80 wt %, or in the alternative, from 55 to 80 wt%, or in the alternative, from 60 to 70 wt %.

The third linear low density polyethylene polymer has a density greaterthan or equal to 0.925 g/cc. All individual values and subranges greaterthan 0.925 g/cc are included herein and disclosed herein; for example,the density of the third linear low density polyethylene polymer canhave a lower limit of 0.925, 0.928, 0.931, 0.934, 0.939 or 0.943 g/cc.In a particular embodiment, the third linear low density polyethylenepolymer has a density less than or equal to 0.98 g/cc. All individualvalues and subranges less than or equal to 0.98 g/cc are included hereinand disclosed herein; for example the upper limit of the density of thethird linear low density polyethylene polymer can be 0.98, 0.97, 0.965,0.962, 0.955, or 0.951 g/cc.

The third linear low density polyethylene polymer has an I₂ less than orequal to 2 g/10 min. All individual values and subranges less than 2g/10 min are included herein and disclosed herein; for example, theupper limit of the I₂ of the third linear low density polyethylenepolymer can be from an upper limit of 2, 1.7, 1.4, 1.1 or 0.9 g/10 min.In a particular embodiment, the I₂ of the third linear low densitypolyethylene polymer is greater than or equal to 0.01 g/10 min. Allindividual values and subranges greater than 0.01 g/10 min are includedherein and disclosed herein; for example the lower limit of the I₂ ofthe third linear low density polyethylene polymer can be 0.01, 0.05,0.1, 0.15 g/10 min.

The invention further provides the second oriented film according to anyembodiment disclosed herein except that the third linear low densitypolyethylene polymer is produced using a Ziegler-Natta catalyst.

The invention further provides the second oriented film according to anyembodiment disclosed herein except that the fourth linear low densitypolyethylene polymer is produced using a molecular catalyst. Molecularcatalyst are homogeneous polymerization catalysts which comprise (a) atransition metal, (b) one or more non-substituted or substitutedcyclopentadienyl ligands, and/or (c) one or more ligands containing atleast one heteroatom, such as, oxygen, nitrogen, phosphorus, and/orsulfur. Molecular catalyst may be immobilized on an inorganic support,such as silica, alumina, or MgCl₂.

The invention further provides the second oriented film according to anyembodiment disclosed herein except that the third linear low densitypolyethylene polymer has a density greater than 0.930 g/cc and an I₂lower than 1 g/10 min.

The invention further provides the second oriented film according to anyembodiment disclosed herein except that the fourth linear low densitypolyethylene polymer has a density less than 0.915 g/cc and an I₂greater than 4 g/10 min.

In another embodiment, the invention provides a third oriented filmcomprising a third polyethylene composition which comprises from 75 toless than 100 wt % of the first polyethylene composition according toany embodiment disclosed herein and/or the second polyethylenecomposition according to any embodiment disclosed herein; and greaterthan 0 to 25 wt % of at least one ethylene-based or propylene-basedpolymer. The third oriented film comprises a third polyethylenecomposition which comprises from 75 to less than 100 wt % of the firstpolyethylene composition according to any embodiment disclosed herein.All individual values and subranges from 75 to less than 100 wt % areincluded herein and disclosed herein. For example, the amount of thefirst polyethylene composition in the third polyethylene composition canbe from a lower limit of 75, 80, 85, 90, or 95 wt % to an upper limit of99.99, 99, 98, 93, 89, 84 or 80 wt %. For example, the amount of thefirst polyethylene composition in the third polyethylene composition canbe from 75 to less than 100 wt %, or in the alternative, from 80 to 99wt %, or in the alternative, from 84 to 99.99 wt %, or in thealternative, from 80 to 90 wt %.

The third polyethylene composition comprises greater than 0 to 25 wt %of at least one ethylene-based or propylene-based polymer. Allindividual values and subranges from greater than 0 to 25 wt % areincluded herein and disclosed herein; for example, the amount of the atleast one ethylene-based or propylene-based polymer can be from a lowerlimit of 0.01, 0.5, 1, 8, 14, 19 or 24 wt % to an upper limit of 0.8, 3,10, 15, 20 or 25 wt %. For example, the amount of the at least oneethylene-based or propylene-based polymer can be from greater than 0 to25 wt %, or in the alternative, from 1 to 15 wt %, or in thealternative, from 16 to 25 wt %, or in the alternative, from 5 to 20 wt%.

The term “ethylene-based polymer,” as used herein, refers to a polymerthat comprises, in polymerized form, a majority amount of ethylenemonomer (based on the weight of the polymer), and optionally maycomprise one or more comonomers. Exemplary ethylene-based polymersinclude low density polyethylene (LDPE, e.g., LDPE having a density from0.917 to 0.924 g/cc and an I₂ of from 0.2 to 75 g/10 min), linear lowdensity polyethylene (LLDPE, e.g., DOWLEX which is an ethylene/1-octenepolyethylene made by The Dow Chemical Company with a typical densitybetween about 0.915 and 0.940 g/cc and a typical I₂ between about 0.5and 30 g/10 min), homogeneously branched, linear ethylene/alpha-olefincopolymers (e.g., TAFMER polymers by Mitsui Chemicals America, Inc. andEXACT polymers by ExxonMobil Chemical (ExxonMobil)), homogeneouslybranched, substantially linear ethylene/alpha-olefin polymers (e.g.,AFFINITY and ENGAGE polymers made by The Dow Chemical Company anddescribed in U.S. Pat. No. 5,272,236, U.S. Pat. No. 5,278,272 and U.S.Pat. No. 5,380,810, the disclosures of which are incorporated herein byreference), catalytic linear statistical olefin copolymers (e.g., INFUSEwhich are polyethylene/olefin block polymers, particularlypolyethylene/alpha-olefin block polymers and especiallypolyethylene/1-octene block polymers, made by The Dow Chemical Companyand described in WO 2005/090425, 2005/090426 and 2005/090427, thedisclosures of which are incorporated herein by reference), and highpressure, free radical polymerized ethylene copolymers such asethylene/vinyl acetate (EVA) and ethylene/acrylate andethylene/methacrylate polymers (e.g., ELVAX. and ELVALOY polymers,respectively, commercially available from E. I. Du Pont du Nemours & Co.(Du Pont)) and ethylene/acrylic (EAA) and ethylene/methacrylic acid(EMAA) polymers (e.g., PRIMACOR EAA polymers commercially available fromThe Dow Chemical Company and NUCREL EMAA polymers commercially availablefrom Du Pont).

The term “propylene-based polymer,” as used herein, refers to a polymerthat comprises, in polymerized form, a majority amount of units derivedfrom propylene monomer (based on the weight of the polymer), andoptionally may comprise one or more comonomers. Exemplarypropylene-based polymers include those available under the tradenameVERSIFY, commercially available from The Dow Chemical Company.

The invention further provides the first oriented film according to anyembodiment disclosed herein except that the first oriented filmaccording to claim 1, wherein the first polyethylene composition hasMW_(HDF>95) greater than 135 kg/mol and I_(HDF>95) greater than 42kg/mol.

The invention further provides the second oriented film according to anyembodiment disclosed herein except that the second oriented filmaccording to claim 6, wherein the first polyethylene composition hasMW_(HDF>95) greater than 135 kg/mol and I_(HDF>95) greater than 42kg/mol.

The invention further provides the third oriented film according to anyembodiment disclosed herein except that the first polyethylenecomposition has MW_(HDF>95) greater than 135 kg/mol and I_(HDF>95)greater than 42 kg/mol.

The invention further provides the first oriented film according to anyembodiment disclosed herein except that the first oriented filmaccording to any embodiment disclosed herein, wherein the first orientedfilm is oriented below the melting point of the first polyethylenecomposition.

The invention further provides the second oriented film according to anyembodiment disclosed herein except that the second oriented filmaccording to any embodiment disclosed herein, wherein the secondoriented film is oriented below the melting point of the secondpolyethylene composition,

The invention further provides the third oriented film according to anyembodiment disclosed herein except that the third oriented filmaccording to any embodiment disclosed herein, wherein the third orientedfilm is oriented below the melting point of the third polyethylenecomposition.

The invention further provides the first oriented film according to anyembodiment disclosed herein except that the first oriented film is abiaxially oriented film.

The invention further provides the second oriented film according to anyembodiment disclosed herein except that the second oriented film is abiaxially oriented film.

The invention further provides the third oriented film according to anyembodiment disclosed herein except that the third oriented film is abiaxially oriented film.

The invention further provides the first biaxially oriented filmaccording to any embodiment disclosed herein except that the firstbiaxially oriented film has been oriented via a sequential orientationprocess with a machine direction (MD) draw ratio greater than 3 and atransverse direction (TD) draw ratio greater than 5.

The invention further provides the second biaxially oriented filmaccording to any embodiment disclosed herein except that the secondbiaxially oriented film has been oriented via a sequential orientationprocess with an MD draw ratio greater than 3 and a TD draw ratio greaterthan 5.

The invention further provides the third biaxially oriented filmaccording to any embodiment disclosed herein except that the thirdbiaxially oriented film has been oriented via a sequential orientationprocess with an MD draw ratio greater than 3 and a TD draw ratio greaterthan 5.

With respect to each of the first, second and third biaxially orientedfilms, all individual values and subranges of an MD draw ratio equal toor greater than 3 are included herein and disclosed herein. For example,the MD draw ratio can be equal to or greater than 3, 3.5, 4, 4.5 or 5.In a particular embodiment, the MD draw ratio is equal to or less than8. All individual values and subranges of equal to or less than 8 areincluded herein and disclosed herein; for example, the MD draw ratio canbe from an upper limit of 8, 7, or 6.

With respect to each of the first, second and third biaxially orientedfilms, all individual values and subranges of a TD draw ratio greaterthan 5 are included herein and disclosed herein. For example, the TDdraw ratio can be greater than 5, 5.5, 6, 6.5 or 7. In a particularembodiment, the TD draw ratio is equal to or less than 13. Allindividual values and subranges of equal to or less than 13 are includedherein and disclosed herein; for example, the TD draw ratio can be froman upper limit of 13, 12, 11, 10, 9 or 8.

The invention further provides the first biaxially oriented filmaccording to any embodiment disclosed herein except that the firstbiaxially oriented film has been oriented via a simultaneous orientationprocess with an MD draw ratio greater than 4 and a TD draw ratio greaterthan 4. In a particular embodiment, the MD draw ratio has an upper limitof 8 and a TD draw ratio upper limit of 8.

The invention further provides the second biaxially oriented filmaccording to any embodiment disclosed herein except that the secondbiaxially oriented film has been oriented via a simultaneous orientationprocess with an MD draw ratio greater than 4 and a TD draw ratio greaterthan 4. In a particular embodiment, the MD draw ratio has an upper limitof 8 and a TD draw ratio upper limit of 8.

The invention further provides the third biaxially oriented filmaccording to any embodiment disclosed herein except that the thirdbiaxially oriented film has been oriented via a simultaneous orientationprocess with an MD draw ratio greater than 4 and a TD draw ratio greaterthan 4. In a particular embodiment, the MD draw ratio has an upper limitof 8 and a TD draw ratio upper limit of 8.

In yet another aspect the invention provides a first co-extruded filmcomprising at least one film layer comprising the first oriented filmaccording to any embodiment disclosed herein.

In yet another aspect the invention provides a first laminated filmcomprising at least one film layer comprising the first oriented filmaccording to any embodiment disclosed herein.

In yet another aspect the invention provides a second co-extruded filmcomprising at least one film layer comprising the second oriented filmaccording to any embodiment disclosed herein.

In yet another aspect the invention provides a second laminated filmcomprising at least one film layer comprising the second oriented filmaccording to any embodiment disclosed herein.

In yet another aspect the invention provides a third co-extruded filmcomprising at least one film layer comprising the third oriented filmaccording to any embodiment disclosed herein.

In yet another aspect the invention provides a third laminated filmcomprising at least one film layer comprising the third oriented filmaccording to any embodiment disclosed herein.

In yet another embodiment, the present disclosure provides a firstoriented film in accordance with any of the embodiments disclosed hereinexcept that the first oriented film exhibits one or more of thefollowing properties: (a) ultimate tensile strength averaged in MD andTD, measured according to ASTM D882, greater than or equal to 40 MPa;and (b) 2% secant modulus averaged in MD and TD, measured according toASTM D882, is greater than or equal to 350 MPa. All individual valuesand subranges of an averaged ultimate tensile strength greater than orequal to 40 MPa are included herein and disclosed herein; for example,the averaged ultimate tensile strength of the first oriented film can begreater than or equal to 40 MPa, or in the alternative, from greaterthan or equal to 75 Mpa, or in the alternative, from greater than orequal to 100 MPa. All individual values and subranges of an averaged 2%secant modulus greater than or equal to 350 MPa are included herein anddisclosed herein; for example, the averaged 2% secant modulus of thefirst oriented film can be greater than or equal to 350 MPa, or in thealternative, from greater than or equal to 750 MPa, or in thealternative, from greater than or equal to 1000 MPa.

In yet another embodiment, the present disclosure provides a secondoriented film in accordance with any of the embodiments disclosed hereinexcept that the second oriented film exhibits one or more of thefollowing properties: (a) ultimate tensile strength averaged in MD andTD, measured according to ASTM D882, greater than or equal to 40 MPa;and (b) 2% secant modulus averaged in MD and TD, measured according toASTM D882, is greater than or equal to 350 MPa. All individual valuesand subranges of an averaged ultimate tensile strength greater than orequal to 40 MPa are included herein and disclosed herein; for example,the averaged ultimate tensile strength of the second oriented film canbe greater than or equal to 40 MPa, or in the alternative, from greaterthan or equal to 75 MPa, or in the alternafirtive, from greater than orequal to 100 MPa. All individual values and subranges of an averaged 2%secant modulus greater than or equal to 350 MPa are included herein anddisclosed herein; for example, the averaged 2% secant modulus of thesecond oriented film can be greater than or equal to 350 MPa, or in thealternative, from greater than or equal to 750 Mpa, or in thealternative, from greater than or equal to 1000 MPa.

In yet another embodiment, the present disclosure provides a thirdoriented film in accordance with any of the embodiments disclosed hereinexcept that the third oriented film exhibits one or more of thefollowing properties: (a) ultimate tensile strength averaged in MD andTD, measured according to ASTM D882, greater than or equal to 40 MPa;and (b) 2% secant modulus averaged in MD and TD, measured according toASTM D882, is greater than or equal to 350 MPa. All individual valuesand subranges of an averaged ultimate tensile strength greater than orequal to 40 MPa are included herein and disclosed herein; for example,the averaged ultimate tensile strength of the third oriented film can begreater than or equal to 40 MPa, or in the alternative, from greaterthan or equal to 75 MPa, or in the alternafirtive, from greater than orequal to 100 MPa. All individual values and subranges of an averaged 2%secant modulus greater than or equal to 350 MPa are included herein anddisclosed herein; for example, the averaged 2% secant modulus of thethird oriented film can be greater than or equal to 350 MPa, or in thealternative, from greater than or equal to 750 MPa, or in thealternative, from greater than or equal to 1000 MPa.

In yet another aspect the invention provides a process for forming anoriented polyethylene film comprising (a) selecting the firstpolyethylene composition according to any embodiment disclosed herein,the second polyethylene composition according to any embodimentdisclosed herein, the third polyethylene composition according to anyembodiment disclosed herein or any combination thereof; (b) forming afilm from the polyethylene composition selected in step (a), (c)orienting the film formed in step (b) via a sequential orientationprocess with an MD draw ratio greater than 3 and a TD draw ratio greaterthan 5. All individual values and subranges of an MD draw ratio greaterthan 3 are included herein and disclosed herein; for example, the MDdraw ration can from a lower limit of 3, 3.5, 4, 4.5 or 5. Allindividual values and subranges of a TD draw ratio greater than 5 areincluded herein and disclosed herein; for example, the MD draw rationcan from a lower limit of 5, 5.5, 6, 6.5 or 7.

EXAMPLES

The following examples illustrate the present invention but are notintended to limit the scope of the invention.

Polyethylene Examples 1-3

Table 1 summarizes the composition of three polyethylenes compositions(PE Comp.) made using a 30 mm co-rotating, intermeshing CoperionWerner-Pfleiderer ZSK-30 twin screw extruder at 250° C. The ZSK-30 hasten barrel sections with an overall length of 960 mm and an L/D ratio of32.

PE Polymer 1 is an LLDPE made using a Ziegler-Natta (ZN) catalyst andhaving a density of 0.935 g/cc and an I₂ of 1.0 g/10 min;

PE Polymer 2 is an LLDPE made using a Ziegler-Natta catalyst and havinga density of 0.935 g/cc and an I₂ of 2.5 g/10 min;

PE Polymer 3 is an LLDPE made using molecular catalyst having a densityof 0.905 g/cc and an I₂ of 15 g/10 min;

LDPE 621I is a low density polyethylene having a density of 0.918 g/ccand an I₂ of 2.3 g/10 min and is commercially available from The DowChemical Company;

LDPE-1 is a low density polyethylene having a density of 0.919 g/cc andan I₂ of 0.47 g/10 min; and

Affinity PL1880 is a polyolefin plastomer having a density of 0.902 g/ccand an I₂ of 1 g/10 min and is commercially available from The DowChemical Company.

33-mil cast sheets were made with a Dr. Collin cast film line (L/D=25and D=30 mm) equipped with a I₂ inch wide flat die. The die gap was 45mil and output rate was about 8 kg/h. Melt temperature was 244° C. anddie temperature was set at 260° C.

Square specimens were cut from the extruded sheet, and biaxiallystretched with a Bruckner Karo IV biaxial stretcher at an engineeringstrain rate of 200%/s based on the original specimen dimensions. Thepreheat time before stretching was fixed to be 60 s. Stretching wasperformed either simultaneously in the two directions or sequentially.In simultaneous stretching, the sheet was stretched in both directionsto a 6.5×6.5 stretch ratio. In sequential stretching, the specimen wasconstrained in cross direction and stretched in machine direction to 4×;after that, it was constrained in machine direction at 4× and stretchedin transverse direction to 8×.

The cast sheets were also stretched into films with an Accupullstretcher. Only simultaneously biaxial orientation was conducted at119.4° C. and an engineering strain rate of 100%/s. The stretch ratiowas 4×8 in MD and TD, respectively. Preheat time was set at 100 s.

In the blown film process, 1 mil monolayer blown film was made using the3-layer Dr. Collin blown film line. The line was comprised of three 25:1L/D single screw extruders, equipped with grooved feed zones. The screwdiameters were 25 mm for the inner layer, 30 mm for the core and 25 mmfor the outer layer. The annular die was 60 mm in diameter and used adual lip air ring cooling system. Die lip gap was set at 2 mm. Blow upratio (BUR) was 2.5 and draw down ratio (DDR) was 31.5. Frost lineheight was 6 inch. Total output rate was around 10.7 kg/hour. Melttemperature and die temperature were set at 215° C.

TABLE 1 PE Comp. Density I₂ MW_(HDF>95) I_(HDF>95) Ex. Component 1Component 2 Component 3 (g/cc) (g/10 min) (kg/mol) (kg/mol) 1 70 wt % PE30 wt % PE None 0.927 1.6 145 65.8 Polymer 1 Polymer 3 2 55 wt % PE 30wt % PE 7.5 wt % 0.926 1.5 152 54.9 Polymer 1 Polymer 3 LDPE 621I; and7.5 wt % LDPE-1 3 55 wt % PE 30 wt % 15 wt % 0.925 1.6 127 37.9 Polymer2 Affinity LDPE PL1880 621I

PE Composition Examples 1 and 2 were used to produce BOPE films. BOPEfilms could not be made from PE Composition Example 3. Biaxialstretchability of the samples was evaluated on a lab-scale tenter framestretcher (Bruckner Karo IV). Results of simultaneous stretching andsequential stretching are summarized in Tables 2 and 3 where S meansSucceed, F means Fail, and N means Not Tested. The success criterion forthe simultaneous stretching is to achieve 6.5× stretch ratio in both MDand TD. The success criterion for the sequential stretching is toachieve 4× stretch ratio in MD and 8× in TD. Inventive Films 1 and 2clearly show a good stretchability and a broad stretching temperaturewindow.

TABLE 2 Oven temperature (° C.) 105 108 110 113 115 117 118 120 123 125127 130 PE Comp. Ex. 1 N N N N N N F S S S F N PE Comp. Ex. 2 N N N N FS S S S F N N PE Comp. Ex. 3 F F F F F F F F F F F F

TABLE 3 Oven temperature (° C.) 105 108 110 113 115 117 118 120 123 125127 130 PE Comp. Ex. 1 N N N N N N N S F N N N PE Comp. Ex. 2 N N N N SS S S F N N N PE Comp. Ex. 3 F F F F F F F F F F F F

TABLE 4 Raw material Fabrication process Process conditions Inventive PETenter frame biaxial Sequentially biaxial orientation. Film 1 Comp.orientation on a Bruckner Draw ratio: 4 × 8 Ex. 2 Karo IV stretcher.Orientation temperature: 115° C. Comparative PE Blown film on a Dr. BUR:2.5 Film 1 Comp. Collin blown film line. DDR: 31.5 Ex. 2 Inventive PETenter frame biaxial Simultaneously biaxial Film 2 Comp. orientation ona Accupull orientation. Ex. 2 stretcher. Draw ratio 4 × 8 Orientationtemperature 120° C.

A polyethylene blown film (Comparative film 1), a biaxially orientedpolyethylene film sequentially stretched to a draw ratio of 4×8 on theBruckner stretcher at 115° C. (Inventive Film 1), and a biaxiallyoriented polyethylene film simultaneously stretched to a draw ratio of4×8 on the Accupull stretcher (Inventive Film 2) and various filmproperties were tested and reported in Table 5.

TABLE 5 Comparative Film 1 Inv. Film 1 Inv. Film 2 Thickness, mil 1 0.90.9 Clarity, % 95 99 99 Haze, % 10.6 2.4 2.4 2% secant modulus in 3221117 569 TD, MPa 2% secant modulus in 261 1010 468 MD, MPa 2% secantmodulus 292 1064 519 averaged in MD and TD, MPa Ultimate tensilestrength 30 153 64 in TD, MPa Ultimate tensile strength 36 135 31 in MD,MPa Ultimate tensile strength 33 144 48 averaged in MD and TD, MPaPuncture peak load (N) 26 Not tested 51

Additional PE Compositions were prepared in a dual polymerizationreactor system. Table 6 provides the reactor conditions for each ofthese dual reactor PE Compositions, PE Compositions 4, 5, 6, and 7. Theproperties of Reactor 2 products were calculated based on the measuredproperties of the Reactor 1 Products and the Final products according to

1/ρ_(f)=w₁/ρ₁+w₂/ρ₂

MI_(f) ^(0.277)=w₁MI₁ ^(0.277)+w₂MI₂ ^(0.277)

where ρ is density, w is weight fraction, MI is melt index (I₂),subscript 1 denotes the reactor 1, subscript 2 denotes the reactor 2 andsubscript f denotes the final product.Tables 6-7 provide certain properties of these PE Compositions. Blendsof these PE Compositions 5-7 with a low density polyethylene were alsoproduced, as described in Table 8.

TABLE 6 Reactor 1 Reactor 1 Reactor 2 Reactor 2 Final Final ProductProduct Product Product Reactor product Product Reactor 1 density I₂Reactor 2 density I₂ 1/Reactor density I₂ catalyst (g/cc) (g/10 min)catalyst (g/cc)* (g/10 min) 2 split, % (g/cc) (g/10 min) PE ZN 0.956 0.6ZN 0.914 3.2 30/70 0.926 1.8 Comp. 4 PE ZN 0.935 0.6 ZN 0.925 3.5 30/700.928 1.9 Comp. 5 PE ZN 0.934 0.6 ZN 0.924 5.5 40/60 0.928 1.9 Comp. 6PE Molecular 0.905 15 ZN 0.939 0.65 35/65 0.927 1.5 Comp. 7 *calculatedas described below

TABLE 7 MW_(HDF > 95) (kg/mol) I_(HDF > 95) (kg/mol) PE Comp. 4 151 63.4PE Comp. 5 152 59.3 PE Comp. 6 154 65.8 PE Comp. 7 149 68.1

TABLE 8 Composition (in weight %) MW_(HDF > 95) (kg/mol) I_(HDF > 95)(kg/mol) PE Comp. 4-a 85% PE Comp. 4 + 15% LDPE 621I 148 51.3 PE Comp.5-a 90% PE Comp. 5 + 10% LDPE 621I 158 56.4 PE Comp. 5-b 85% PE Comp.5 + 15% LDPE 621I 158 53.3 PE Comp. 6-a 90% PE Comp. 6 + 10% LDPE 621I156 59.0 PE Comp. 6-b 85% PE Comp. 6 + 15% LDPE 621I 158 59.7 PE Comp.7-a 90% PE Comp. 7 + 10% LDPE 621I 150 61.9 PE Comp. 7-b 85% PE Comp.7 + 15% LDPE 621I 153 60.9

Table 9 provides the simultaneously biaxial orientation results (testedby the Bruckner biaxial stretcher) for films using a MD draw ratio of6.5× and a TD draw ratio of 6.5× produced using several of the PECompositions shown in Tables 6 and 8.

TABLE 9 Oven temperature (° C.) 110 113 115 117 120 122 125 127Inventive Film N F S S S S S F 4-a Inventive Film N F F F S S F N 5Inventive Film N F F S S S F N 5-a Inventive Film F F F S S S F N 5-bInventive Film N F F F F S F N 6 Inventive Film N F F F S S F N 6-aInventive Film F F S S S S F N 6-b Inventive Film N F F F F F S F 7Inventive Film N F F F F S F N 7-a Inventive Film F F F F S S F N 7-b

Table 10 provides the sequentially biaxial orientation results (testedby the Bruckner biaxial stretcher) for films using a MD draw ratio of 4×and a TD draw ratio of 8×, produced using several of the PE Compositionsshown in Tables 6 and 8.

TABLE 10 Oven temperature (° C.) 110 113 115 117 120 122 125 127Inventive Film N N S S S S S F 4-a Inventive Film N F S S S S F N 5-aInventive Film N F S S S S F N 5-b Inventive Film N F S S S S S F 6-aInventive Film N F S S S S S F 6-b Inventive Film N F S S S S S F 7-aInventive Film N F S S S S S F 7-b

Test Methods

Melt index, or I₂, was measured in accordance with ASTM D 1238,condition 190° C./2.16 kg. Density was first measured according to ASTMD 1928. Density measurements were made using ASTM D792, Method B.

Tensile properties in both directions were determined using ASTM D882 aswas the 2% secant modulus. 2% secant modulus averaged in MD and TD=(2%secant modulus in MD +2% secant modulus in TD)/2. Ultimate tensilestrength averaged in MD and TD=(Ultimate tensile strength in MD+Ultimatetensile strength in TD)/2. Puncture test was performed using a modifiedASTM D 5748 with a 0.5″ diameter stainless steel probe.

Film gloss at 20° was determined using ASTM D2457 while haze was donevia ASTM D1003 and clarity by ASTM D1746.

Crystallization Elution Fractionation (CEF) is described by Monrabal etal, Macromol. Symp. 257, 71-79 (2007). The instrument is equipped withan IR-4 detector (such as that sold commercially from PolymerChar,Spain) and a two angle light scattering detector Model 2040 (such asthose sold commercially from Precision Detectors). The IR-4 detectoroperates in the compositional mode with two filters: C006 and B057. A 10micron guard column of 50×4.6 mm (such as that sold commercially fromPolymerLabs) is installed before the IR-4 detector in the detector oven.Ortho-dichlorobenzene (ODCB, 99% anhydrous grade) and2,5-di-tert-butyl-4-methylphenol (BHT) (such as commercially availablefrom Sigma-Aldrich) are obtained. Silica gel 40 (particle size 0.2˜0.5mm) (such as commercially available from EMD Chemicals) is alsoobtained. The silica gel is dried in a vacuum oven at 160° C. for abouttwo hours before use. Eight hundred milligrams of BHT and five grams ofsilica gel are added to two liters of ODCB. ODCB containing BHT andsilica gel is now referred to as “ODCB.” ODBC is sparged with driednitrogen (N₂) for one hour before use. Dried nitrogen is obtained bypassing nitrogen at <90 psig over CaCO₃ and 5Å molecular sieves. Samplepreparation is done with an autosampler at 4 mg/ml under shaking at 160°C. for 2 hours. The injection volume is 300 μl. The temperature profileof CEF is: crystallization at 3° C./min from 110° C. to 30° C., thermalequilibrium at 30° C. for 5 minutes (including Soluble Fraction ElutionTime being set as 2 minutes), and elution at 3° C./min from 30° C. to140° C. The flow rate during crystallization is 0.052 ml/min. The flowrate during elution is 0.50 ml/min. The data are collected at one datapoint/second.

The CEF column is packed with glass beads at 125 μm±6% (such as thosecommercially available from MO-SCI Specialty Products) with ⅛ inchstainless tubing according to US 2011/0015346 A1. The internal liquidvolume of the CEF column is between 2.1 and 2.3 mL. Temperaturecalibration is performed by using a mixture of NIST Standard ReferenceMaterial Linear polyethylene 1475a (1.0 mg/ml) and Eicosane (2 mg/ml) inODCB. The calibration consists of four steps: ⁽¹⁾ Calculating the delayvolume defined as the temperature offset between the measured peakelution temperature of Eicosane minus 30.00° C.; ⁽²⁾ Subtracting thetemperature offset of the elution temperature from the CEF rawtemperature data. It is noted that this temperature offset is a functionof experimental conditions, such as elution temperature, elution flowrate, etc.; ⁽³⁾ Creating a linear calibration line transforming theelution temperature across a range of 30.00° C. and 140.00° C. such thatNIST linear polyethylene 1475a has a peak temperature at 101.00° C., andEicosane has a peak temperature of 30.00° C., ⁽⁴⁾ For the solublefraction measured isothermally at 30° C., the elution temperature isextrapolated linearly by using the elution heating rate of 3° C./min.The reported elution peak temperatures are obtained such that theobserved comonomer content calibration curve agrees with thosepreviously reported in U.S. Pat. No. 8,372,931.

A linear baseline is calculated by selecting two data points: one beforethe polymer elutes, usually at temperature of 26° C., and another oneafter the polymer elutes, usually at 118° C. For each data point, thedetector signal is subtracted from the baseline before integration.

Molecular Weight of High Density Fraction (MW_(HDF>95)) and High DensityFraction Index (I_(HDF>95))

The polymer molecular weight can be determined directly from LS (lightscattering at 90 degree angle, Precision Detectors) and theconcentration detector (IR-4, Polymer Char) according to theRayleigh-Gans-Debys approximation (A. M. Striegel and W. W. Yau, ModernSize-Exclusion Liquid Chromatography, 2^(nd) Edition, Page 242 and Page263, 2009) by assuming a form factor of 1 and all the virialcoefficients equal to zero. Baselines are subtracted from the LS (90degree) and IR-4 (measurement channel) chromatograms. For the wholeresin, integration windows are set to integrate all the chromatograms inthe elution temperature (temperature calibration is specified above)ranging from 25.5 to 118° C. The high density fraction is defined as thefraction that has an elution temperature higher than 95.0° C. in CEF.Measuring the MW_(HDF>95) and I_(HDF>95) includes the following steps:

-   (1) Measuring the interdetector offset. The offset is defined as the    geometric volume offset between LS detector with respect to the IR-4    detector. It is calculated as the difference in elution volume (mL)    of the polymer peak between the IR-4 and LS chromatograms. It is    converted to the temperature offset by using the elution thermal    rate and elution flow rate. A high density polyethylene (with no    comonomer, melting index I₂ of 1.0, polydispersity or molecular    weight distribution M_(w)/M_(n) approximately 2.6 by conventional    gel permeation chromatography) is used. The same experimental    conditions as the CEF method above are used except for the following    parameters: crystallization at 10° C./min from 140° C. to 137° C.,    thermal equilibrium at 137° C. for 1 minute as the Soluble Fraction    Elution Time, and elution at 1° C./min from 137° C. to 142° C. The    flow rate during crystallization is 0.10 ml/min. The flow rate    during elution is 0.80 ml/min. The sample concentration is 1.0    mg/ml.-   (2) Each data point in the LS chromatogram is shifted to correct for    the interdetector offset before integration.-   (3) Molecular weight at each retention temperature is calculated as    the baseline subtracted LS signal/the baseline subtracted IR4    signal/MW constant (K)-   (4) The baseline subtracted LS and IR-4 chromatograms are integrated    in the elution temperature range of 95.0 to 118.0° C.-   (5) The Molecular weight of the high density fraction (MW_(HDF>95))    is calculated according to

MW_(HDF>95)=∫₉₅ ¹¹⁸Mw·C·dT/∫₉₅ ¹¹⁸ C·dT

where Mw is the molecular weight of the polymer fraction at the elutiontemperature T and C is the weight fraction of the polymer fraction atthe elution temperature T in the CEF, and

∫₂₅ ¹¹⁸ C·dT=100%

-   (6) High density fraction index (I_(HDF>95)) is calculated as

I_(HDF>95)=∫₉₅ ¹¹⁸ Mw·C·dT

where Mw in is the molecular weight of the polymer fraction at theelution temperature Tin the CEF.

The MW constant (K) of CEF is calculated by using NIST polyethylene1484a analyzed with the same conditions as for measuring interdetectoroffset. The MW constant (K) is calculated as “(the total integrated areaof LS) of NIST PE1484a/(the total integrated area) of IR-4 measurementchannel of NIST PE 1484a/122,000”.

The white noise level of the LS detector (90 degree) is calculated fromthe LS chromatogram prior to the polymer eluting. The LS chromatogram isfirst corrected for the baseline correction to obtain the baselinesubtracted signal. The white noise of the LS is calculated as thestandard deviation of the baseline subtracted LS signal by using atleast 100 data points prior to the polymer eluting. Typical white noisefor LS is 0.20 to 0.35 mV while the whole polymer has a baselinesubtracted peak height typically around 170 mV for the high densitypolyethylene with no comonomer, I₂ of 1.0, polydispersity M_(w)/M_(n)approximately 2.6 used in the interdetector offset measurements. Careshould be maintained to provide a signal to noise ratio (the peak heightof the whole polymer to the white noise) of at least 500 for the highdensity polyethylene.

We claim:
 1. An oriented film comprising a polyethylene compositionwhich comprises: from 50 to 80 wt % of a linear low density polyethylenepolymer having a density greater than 0.925 g/cc and an I₂ less than 2g/10 min; and from 50 to 20 wt % of an additional linear low densitypolyethylene polymer having a density lower than 0.920 g/cc and an I₂greater than 2 g/10 min; wherein the polyethylene composition has an I₂from 0.5 to 10 g/10 min and a density from 0.910 to 0.940 g/cc whereinthe oriented film is produced by a tenter frame process.
 2. The orientedfilm according to claim 1, wherein the linear low density polyethylenepolymer is produced using a Ziegler-Natta catalyst.
 3. The oriented filmaccording to claim 1, wherein the additional linear low densitypolyethylene polymer is produced using a molecular catalyst.
 4. Theoriented film according to claim 1, wherein the linear low densitypolyethylene polymer has a density greater than 0.930 g/cc and an I₂lower than 1 g/10 min.
 5. The oriented film according to claim 1,wherein the additional linear low density polyethylene polymer has adensity less than 0.915 g/cc an I₂ greater than 4 g/10 min.
 6. Theoriented film according to claim 1, wherein the polyethylene compositionhas an MW_(HDF>95) greater than 135 kg/mol and I_(HDF>95) greater than42 kg/mol.
 7. The oriented film according to claim 1, wherein theoriented film is oriented below the melting point of the polyethylenecomposition.
 8. The oriented film according to claim 1, wherein theoriented film is a biaxially oriented film.
 9. The biaxially orientedfilm according to claim 8 which has been oriented via a sequentialorientation process with an MD draw ratio greater than 3 and a TD drawratio greater than
 5. 10. The biaxially oriented film according to claim8 which has been oriented via a simultaneous orientation process with anMD draw ratio greater than 4 and a TD draw ratio greater than
 4. 11. Aco-extruded film comprising at least one film layer comprising theoriented film according to claim
 1. 12. A laminated film comprising atleast one film layer comprising the oriented film according to claim 1.13. The biaxial oriented film according to claim 8 wherein the biaxialoriented film exhibits one or more of the following properties: ultimatetensile strength averaged in MD and TD, measured according to ASTM D882,greater than or equal to 40 MPa; and 2% secant modulus averaged in MDand TD, measured according to ASTM D882, greater than or equal to 350MPa.